A nationwide, multi-billion pound project to roll-out the European Rail Traffic Management System across the UK railway network is due to begin in 2011 , according to a newly published government strategy document (link below.)
http://www.rmtbristol.org.uk/2007/10/2017_start_date_for_great_west.html#more

The ERTMS National Implementation Plan has been submitted to the European Commission to comply with a series of EU railway directives and commits the UK to installing the next-generation system on 72% of the National Rail network between now and 2038.

ERTMS is currently being trialled on the Cambrian Line in Wales but once adopted on busier routes would have the potential to increase line capacity for a relatively modest investment in infrastructure. The technology would replace conventional trackside signals with high-tech beacons which would communicate with in-cab equipment , allowing trains to safely travel more closely together and potentially at higher speeds.

Under the government’s rail strategy , new trains will be ordered with ERTMS capability and lineside signaling infrastructure will by upgraded to the new technology when renewals are due.

New rolling stock , including the recently approved Thameslink Programme fleet , Crossrail trains and Intercity Express carriages will be fitted with ERTMS equipment. The Brighton Main Line is scheduled to carry the first ERTMS-ready trains from 2011 although trackside infrastructure is not due to be ready until 2021 at the earliest.

The first major infrastructure implementation is due to start in 2017 on the Great Western route , although the Midland Main Line is expected to be the first inter-city route to fully implement ERTMS , some time between 2021 and 2023. The Department for Transport expects the majority of ERTMS work on the Great Western and East Coast Main Lines to be complete by 2025 , although infrastructure work may drag on for another decade.